Cyanoacrylate activators

Acrylic Adhesives. Acryhc stmctural adhesives can be classified into three major types the surface-activated acryhcs (anaerobics), the surface-activated second-generation acryhcs, and the cyanoacrylates. 

Cyanoacrylate adhesives (Super-Glues) are materials which rapidly polymerize at room temperature. The standard monomer for a cyanoacrylate adhesive is ethyl 2-cyanoacrylate [7085-85-0], which readily undergoes anionic polymerization. Very rapid cure of these materials has made them widely used in the electronics industry for speaker magnet mounting, as weU as for wire tacking and other apphcations requiring rapid assembly. Anionic polymerization of a cyanoacrylate adhesive is normally initiated by water. Therefore, atmospheric humidity or the surface moisture content must be at a certain level for polymerization to take place. These adhesives are not cross-linked as are the surface-activated acryhcs. Rather, the cyanoacrylate material is a thermoplastic, and thus, the adhesives typically have poor temperature resistance. 

Interestingly, this same effect has been observed for the addition of a rubber toughening agent to ethyl cyanoacrylate-based adhesives, as was reported previously. The rubber must contain enough latent acid functionality on the polymer backbone or in an additive to inhibit the thermally activated decomposition of the alkyl cyanoacrylate adhesive polymer. 

Because of the need for basic initiators, cyanoacrylate adhesives do not perform well on acidic surfaces, such as wood. However, the addition of sequestering agents, such as crown ethers [30], 10, or calixarenes [31], 11, and others [32] to the adhesive improves the reactivity of the adhesive on less active surfaces. 

Components/ mechanism of action Light-activated polyethylene-glycol (PEG) polymer sealant for lung tissue. Monomeric (2-octyl cyanoacrylate) formulation tissue adhesive for skin closure. Bovine albumin cross-linked with gluteraldehyde tissue adhesive/sealant. 

N Ammoury, H Fessi, JP Devissaguet, M Du-brasquet, S Benita. Jejunal absorption, pharmacological activity, and pharmacokinetic evaluation of indomethacin-loaded poly(d,l-lactide) and poly(-isobutyl-cyanoacrylate) nanocapsules in rats. Pharm Res 8 101-105, 1991. 

Alyautdin R, Gothier D, Petrov V, Kharkevich D, Kreuter J (1995) Analgesic activity of the hexa-peptide dalargin adsorbed on the surface of polysorbate 80-coated poly(butyl cyanoacrylate) nanoparticles. Eur J. Pharm Biopharm 41 44 48. 

Methyl 2-cyanoacrylate was positive in the Ames test with and without activation by metabolic enzymes. ... 

The cyanoacrylate molecule has the electron-withdrawing groups, cyano and ester moieties, attached to the same carbon. They activate the carbon atom to nucleophilic attack from the moisture on the surface of the substrate, and this... 

A special-purpose adhesive that forms an exceedingly strong bond to metals and many other materials, including careless experimenters, is cyanoacrylate contact cement, available as Eastman 910 Adhesive and Super Glue (Woodhill Chemical). It is expensive, but only small amounts are needed. In this cement, the material polymerizes rapidly without an added activator. It is not void filling, and a 0.001 in.-thick film yields the best bond. Do not buy more than you will need in a few months since it slowly deteriorates store in the refrigerator. 

Both, the liquid and cured 2-cyanoacrylic esters support combustion. These adhesives should not be used near sparks, heat, or open flame, or in areas of acute fire hazard. Highly exothermic polymerization can occur from direct addition of catalytic substances such as water, alcohols, and bases such as amines, ammonia, or caustics, or from contamination with any of the available surface activator solutions. 

Overall polymerization rates which are equated with the rate of propagation were first order in monomer and very fast. At -78 °C the rate constants fell between 1.0 and 3.4 x 1051 mol-1 s 1. Activation energies were very small, 2.2 and 5.5 kJ mol-1 for ethyl (EGA) and butyl (BCA) cyanoacrylates, respectively. Of a range of ammonium, phosphonium, and alkali metal salts only lithium bromide significantly reduced the rate of polymerization. Ogawa and Romero16 found the rate of acrylonitrile polymerization increased by the presence of an ammonium salt but reduced by lithium chloride. There may be a specific interaction between cyano substituted carbanions and the lithium cation. 

L. Montanaro, C. R. Arciola, E. Cenni, Cytotoxicity, blood compatibility and antimicrobial activity of two cyanoacrylate glues for surgical use, Biomaterials., 22 [1] 59-66 (2001). 

Many drug carriers are made of hydrophobic materials such as lipids and poly(butyl cyanoacrylate). It will be thermodynamically unstable for submicron particles made of these materials to remain dispersed in an aqueous environment such as blood circulation. Surfactants or block co-polymers are therefore routinely included in these formulations to prevent particle aggregation. Studies showed that a number of these agents, most noticeably the nonionic surfactants such as polysorbates (also known as Tweens) and Tritons and block co-polymers such as poloxamers (also known as Pluronics), may inhibit the ABC transporters [97-99]. As previously discussed, ABC transporters interact with their substrates in the lipid bilayers of the plasma membrane. Surfactants can disrupt the arrangement of the lipid bilayer expressing the transporters and subsequently inhibit their drug efflux activities [97, 100]. It... 

Cyanoacrylate adhesives can be defined as single-component chemically active liquids that react very rapidly with moisture or other weakly alkahne materials to form clear, hard solids. Their important characteristics are ... 

Although it is not essential to understand the chemistry of cyanoacrylate polymerization to be able to use these adhesives, knowing that a chemical reaction is taking place helps the user to understand how application conditions affect their performance. Consider the fact that the common polymers, such as polyethylene, polystyrene, and poly(vinyl chloride) (PVC), are made in sophisticated reactors. Parameters such as temperature, monomer concentration, and amount of activator are carefully controlled. 

A typical cure curve for 100-cP methyl cyanoacrylate is shown in Fig. 5. The speed of cure is influenced by the thickness of the bond, the activity of the surface, and the designed speed of the adhesive. 

Since bases are catalysts for the curing reaction and acids are stabilizers for the cyanoacrylates, the pH value of the surface will control the cure speed. Surfaces that tend to be acidic will cure slowly compared to a neutral surface, which in turn will cure more slowly than an alkaline surface. In most applications the objective is to speed the cure therefore, all the commercially available activators are weak bases dissolved in a volatile carrier. Applying an activator to a surface places a layer of the weak base in position to initiate the cure. Since they are stronger bases than moisture, they are able to neutralize the stabilizer systems in the adhesive more effectively, and thus they can tolerate larger gaps than would be possible with moisture alone. In general, the fixturing time is 10 times faster with activator than without it. Even with activator, the effect of the gap is clear (see Table 4). 

The new range of surface-insensitive cyanoacrylates provides ultrafast cures independent of gap. In addition, these cyanoacrylates will rapidly bond acidic and low-energy surfaces. The fast cure also minimizes the occurrence of frosting and fogging. Table 6 shows a comparison of these new surface-insensitive materials compared to a standard ethyl-grade cyanoacrylate. These products are also suited to bonding various wood substrates and porous surfaces without the use of activators. 

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